I have a few questions about candling. First of all i wasn't planning on candling till day ten, then I decided day seven, then I bought a (really crappy) candler today and it's instructions said start on day four and since that's what I'm at and I'm such a meddler, I took it as a sign that I should do it today! (I set them Sunday morning so that's day four right? Or five?)
With that said, these are buff Orpington eggs so, brown but pretty light. This candler isn't even as bright as my phones flashlight though so I can barely see anything.
Eight looked either totally clear or I could see a small dark spot about the size of a nickel which appeared to be a yolk but only if I really looked for it. I turned the eggs fat side down tryin to see if I could see any better and still couldn't and then I realized I had no idea if that is a no-no, to turn them upside down or not?!
The other 16 eggs had an obvious dark shadow all the way around the top 1/3 to 1/2 and then were light or see through on the bottom half. The very lightest egg I have I could actually see veins but all the others I could only see the dark shadow.
I don't know what to make of the fact that most of them were dark all the way around the top, I couldn't see an air cell, are those ones still viable, are they dead? There wasn't a darker ring like a blood ring, it was just shadowy on top and not shadowy on the bottom. Are the ones that were clear save for a small dark spot dead, or developing properly, or ??? if they were alive, did I kill them by turning them upside down?

IMO, there are two things you are looking for when candling.

Is the egg completely clear? My eggs are darker, not full Black Copper Maran dark brown, but still dark. This makes it hard to candle, but when they are infertile the light makes the entire egg glow and there is no sign of any darker area. Those I know are infertile because I have checked every one that I thought were infertile.

Is there a line around the air sac? When an egg dies while developing (say before day 12 or so), the blood from the developing embryo floats to the top (air sac end, fat end) of the egg making the line. These are the eggs that might explode, so you definitely want them out of your bator.

As for turning eggs, as long as you aren't doing it violently, turning will not harm them. Whether you turn end over end or just turn them around, its all good. Fact is, if you put an egg down with space around it, it will naturally roll to its right position as the air sac area has no weight to it. If you are setting eggs on an angle (as you would in an egg turner or carton), always set the fat end up.

As far as porosity goes, the problem with porous eggs is that they loose too much moisture compared to non-porous eggs. If you were to weigh a porous and non-porous daily, you'd see the weight gap increasing. That makes it hard to control humidity. Humidity makes moisture come out of the egg, which causes the air sac to increase with the air that is displacing the lost moisture. The sac needs to have enough air to allow the chick to breath after its done its internal pip (breaking a hole into the air sac before it breaks a hole in the shell). When you lower the humidity, more moisture leaves the egg, higher humidity, less moisture. When you have porous and non-porous together, the humidity will affect each differently. But FWIW, both could hatch perfectly fine, if hatched separately.

If most of your eggs are porous, don't set non-porous eggs with them.

There are lots of "egg incubation charts" on the web, just google that term. The first thing to develop is the eye, around day 5, which will appear as a small dark spot. So candling too early doesn't show you anything really.

Patience is the hardest part of incubating, so have fun watching...;-]

Patience is the hardest part of incubating, so have fun watching...;-]

Isn't that the truth! In your opinion and experience - how do you personally calculate day 21? Example: I set these eggs at 6am Thu 1/14/16 - would day 21 be Thu 2/4 or Fri 2/5? I am trying to determine if lockdown is Mon or Tue next week. Or does it really make a huge difference?

~~"To a man who keeps hens, all poultry lore is exciting and endlessly fascinating."~~ EB White

Machinfarm, I am new too and last night candled my eggs at 16 days and turned some up side down and worried if that was ok, so I'm glad you joined us, we can all learn from each other's questions and answers🙃

Isn't that the truth! In your opinion and experience - how do you personally calculate day 21? Example: I set these eggs at 6am Thu 1/14/16 - would day 21 be Thu 2/4 or Fri 2/5? I am trying to determine if lockdown is Mon or Tue next week. Or does it really make a huge difference?

For me, there's Day 0, the day I set the eggs in the bator. Plus I always set at noon, so my hatching starts just before 21 days have passed, and in this case of my current setting, has continued into day 23

I had 19 hatch in the last 6 hours of Day 20, 27 more on Day 21, and 4 more on Day 22. I have one egg that has not yet been zipped so it will likely arrive after noon, making it a Day 23 hatch.

To maybe make it clearer, I set my eggs at noon on 1/6/16. Day 21 began at noon on 1/27/16.

If your weight loss has been kept close to ideal (2% of original egg weight every 3 days), then you are unlikely to have premature births...so it won't make much difference if you lockdown on Day 18 or 19. Besides, lockdown isn't needed until you have a pipped egg, as that's when a sudden drop in humidity stands a chance of causing the membrane to dry out. Even then, the drop would have to be for more than, I dunno, 15 minutes or more for it to have that impact. My bator recovers humidity very quickly, so I am less concerned that some others may be. Once I start getting hatchlings I am comfortable removing the tray from the bator, removing the dry chicks, and handling the eggs which don't appear to have a pip (I run my hands over them to feel for protrusions that may be pips, and to remove any pieces of shell from other eggs) and then put the tray back. Since I have two trays, that time is doubled. Of course I keep the bator door closed while I do this, but the eggs are out of the bator for 5 minutes or so.

It is really hard for you to harm a hatching egg, so don't fret too much. You've got to satisfy your curiosity, go through some experiences, and realize that not every egg is destined to survive. The more eggs you have in an incubator, the more variables get involved, the more likely you're going to see the differences in eggs hatching.

For me, there's Day 0, the day I set the eggs in the bator. Plus I always set at noon, so my hatching starts just before 21 days have passed, and in this case of my current setting, has continued into day 23

I had 19 hatch in the last 6 hours of Day 20, 27 more on Day 21, and 4 more on Day 22. I have one egg that has not yet been zipped so it will likely arrive after noon, making it a Day 23 hatch.

To maybe make it clearer, I set my eggs at noon on 1/6/16. Day 21 began at noon on 1/27/16.

If your weight loss has been kept close to ideal (2% of original egg weight every 3 days), then you are unlikely to have premature births...so it won't make much difference if you lockdown on Day 18 or 19. Besides, lockdown isn't needed until you have a pipped egg, as that's when a sudden drop in humidity stands a chance of causing the membrane to dry out. Even then, the drop would have to be for more than, I dunno, 15 minutes or more for it to have that impact. My bator recovers humidity very quickly, so I am less concerned that some others may be. Once I start getting hatchlings I am comfortable removing the tray from the bator, removing the dry chicks, and handling the eggs which don't appear to have a pip (I run my hands over them to feel for protrusions that may be pips, and to remove any pieces of shell from other eggs) and then put the tray back. Since I have two trays, that time is doubled. Of course I keep the bator door closed while I do this, but the eggs are out of the bator for 5 minutes or so.

It is really hard for you to harm a hatching egg, so don't fret too much. You've got to satisfy your curiosity, go through some experiences, and realize that not every egg is destined to survive. The more eggs you have in an incubator, the more variables get involved, the more likely you're going to see the differences in eggs hatching.

Thanks ambe0487, I didn't know if I could postpone lockdown a day if the air sacs were too small.

2nd incubator coming today, time to relax like you said, and just learn from my 1st attempt.

You can postpone if you'd like. You don't typically see any action on day on day 18 or 19 so if you'd like you can wait until day 19 to up the humidity. Some people wait until they see an external pip to increase their humidity. I say do what you feel is right!

I don't follow air sacs myself now, I use egg weight instead. But when I did follow air sacs, the key indicator they were getting read to pip is when one side of the air sac draws down towards the middle (lengthwise) of the egg. At that point the air sac will be far more oval in shape than yours appear to be now.

Also, comparing air sac size is more about the progress, than some set size.